What Are ‘Superspreader’ Events and Why Should You Avoid Them?

An infectious disease expert explains
super spreader, pandemic, covid-19, virus, social distancing

One disturbing trend of coronavirus (COVID-19) pandemic has been the growing focus on “superspreader events,” gatherings of people where even just a single infection spurs a large outbreak among attendees.

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Weddings, funerals and even large family parties (like birthdays or holiday dinners) are a few examples of regular events that turn into superspreaders, though there are plenty of other examples, too. Whatever the situation, though, the more people there are, the higher the risk becomes.

We talked to infectious disease doctor Donald Dumford, MD, about coronavirus superspreader events, why you should avoid them and what you should you do if you end up at one anyway.

What is a ‘superspreader’?

One of the confounding things about superspreader events is that they don’t have exact criteria. It’s entirely possible to have a large gathering of people where very few people (or even none) contract the virus while a family gathering of a dozen people could spread the virus to everyone.

“When you see a large event where there’s a greater amount of transmission than would be expected, that qualifies as a superspreader,” says Dr. Dumford.

He explains that the standard experts are following now says that an infected person at a gathering can be expected to infect two to three people (an average of 2.5) and there’s an infection rate of about 20% among family members from an infectious person.

“When you see an event where that rate is higher, that’s usually what you’d consider a superspreader event,” he adds. As an example, he notes the now-well-known study from Washington State that focused on a 61-person choir practice in which a single infected member caused 32 confirmed infections and 20 additional probable cases among the other members.

“Normally,” Dr. Dumford says, “you would expect two or three people, the closest to the infected individual, to get sick from that interaction. Instead, it was at least 3 times that, possibly 5 times.”

How do superspreader events occur?

It all comes down to how the virus spreads. “This virus is predominantly transmitted by close contact droplets,” Dr. Dumford reminds us. “It’s going to be spread by that person you’re sitting with at a table who you’re talking with for an extended period of time.”

Take that choir practice mentioned above. Over the course of two-and-a-half hours, the infected asymptomatic patient was constantly projecting virus-laden droplets into the air. And given the close quarters and indoor nature of the practice, there was plenty of time for those droplets to circulate and infect dozens of others in the room, not just those in the immediate vicinity.

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When we speak or cough or sing, we can propel these virus-infected droplets around six feet (even more if you sneeze). But Dr. Dumford points out that superspreader events probably occur when much smaller virus-laden droplets are able to float in the air for a longer period of time, spreading over a longer distance and becoming easier to inhale. This is why crowded, indoor gatherings are probably the most likely to become super spreader events.

Why your “bubble” doesn’t matter

Superspreaders that come from family events often catch those infected off-guard because they believe their family to be something of a safe “bubble,” a confined group of people they’re around often and won’t cause an outbreak. But, as Dr. Dumford notes, many don’t quite fully comprehend the fullest, strictest “bubble” concept.

“There are definitely big family gatherings, like a birthday party or a wedding, that can be a good example of a superspreader,” he says. “They may be your family, but often you don’t all live under the same roof. There’s still a risk because you don’t know if every member has completely isolated themselves from other people, whether they’ve been hanging out with friends or going to restaurants.”

He adds, “You really can’t be sure about them unless you’re under the same roof with them all the time. It’s not really a ‘bubble’ unless that unit is the only one everyone interacts with.”

Other potential superspreader events to avoid

It’s not just family gatherings that can cause these widespread outbreaks, though. “These are situations where you’re going from that predominant transmission to that aerosol transmission thanks to air currents,” Dr. Dumford says.

“The worst-case scenarios are events where a large number of people are clustered together, talking or singing or some other sort of increased activity, especially in a poorly ventilated setting,” he adds. This could be a conference or even a religious service.

“Outdoor gatherings are safer than indoor gatherings and indoor gatherings with the windows open and an airflow going through are better than not,” he adds.

Concerts, he says, where people are often dancing and singing, are high risk locations as are being around a large group of people like in a noisy, crowded bar. “You’re having to talk loud or yell and there’s probably a lot of laughing, so that’s going to propel those droplets and get them circulating,” Dr. Dumford says.

How to keep safe                                      

No matter the setting, though, there’s still an inherent risk. Masks and social distancing will cut that risk way down, especially in outdoor settings, but Dr. Dumford points out that with the spread of the virus being so high, there’s always a risk in crowds.

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“We do our best to stay safe, but the more people you’re close to, you’re in contact with, the higher the risk goes even if you’re doing everything possible,” he says. “You can rely on yourself to wear a mask and think you’re protected but in the community, your cloth mask is more about source control than exposure prevention.”

For example, in a restaurant when people are constantly taking off their masks to eat, there’s a greater risk of the virus spreading even in those moments. A recent study by the Centers for Disease Control (CDC) noted the increased risk of coronavirus infection in patrons who ate at restaurants.

“Even if you’re doing everything you should be doing,” Dr. Dumford adds, “when you’re in a large group of people, it can be hard to rely on everyone else around you to do what they should be doing, too. They may wear a mask incorrectly or not wear a mask at all. It’s best to avoid these large gatherings altogether.”

After a big event                                     

Let’s say, despite the warnings, you decide to attend an event or maybe you go to a gathering expecting it to be small but it turns out to be quite big. What should you do afterward, especially if you find out someone else at the gathering tests positive for coronavirus?

Getting tested

According to Dr. Dumford, whether or not you should get tested depends on the situation. “We know it can take anywhere from 4 to 14 days for the virus to incubate and for you to potentially show symptoms. But if you get tested 2 days later, the test isn’t likely to detect the virus.”

Additionally, you may not be infected or you may be asymptomatic. If you don’t show symptoms, it’s probably best to stay isolated and quarantine. If you do show symptoms, though, contact your healthcare provider immediately for next steps.

Isolation

Even if you show no symptoms, you’ll want to quarantine or self-isolate for 14 days. “I would be sure to wear a mask even when you’re inside your own home and around family members that you wouldn’t normally mask-up for,” Dr. Dumford adds.

“You need to avoid exposing others, especially those that might have compromised immune systems,” he adds.

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